In an article by the guardian Uploads from iPhones using the Facebook app will push all your contacts onto Facebook's servers - where they'll be matched against any and everyone. Worried at all?
Facebook: contains more phone numbers than meet the eye
If you have a friend on Facebook who has used the iPhone app version to access the site, then it's very possible that your private phone numbers - and those of lots of your and their friends - are on the site.
The reason: Facebook's "Contact Sync" feature, which synchronises your friends' Facebook profile pictures with the contacts in your phone.
Except that it doesn't do that on your phone. Oh no. Because that would be wrong, to pull the photos down from Facebook and put them on your phone. That would breach Facebook's terms of service.
Instead, what Facebook's app does it that it imports all the names and phone numbers you have on your (smart)phone, uploads them to Facebook's Phonebook app (got a Facebook account? Here's your Phonebook).
Pause for a moment and go and look at it. Did you know those numbers? Did you collect them? Despite the reassuring phrase there - "Facebook Phonebook displays contacts you have imported from your phone, as well as your Facebook friends" - it's absolutely not true. I know because there are numbers there which I don't have. OK, perhaps the people who own them added them; but that's not clear either. So how did they get there? Because it only takes one person to upload another person's number, and the implication is that it's going to be shared around everywhere.
The implications are huge, and extremely worrying. All it takes is for someone's Facebook account to be hacked (perhaps via their phone being stolen) and lots of personal details are revealed.
Kurt von Moos, who first wrote about this earlier this year (since when Facebook has revised its privacy statement, but not altered what goes on in this way) says that there are a number of reasons to be concerned. As he puts it:
von Moos continues:
von Moos concludes: "There are some contacts and phone numbers who's privacy I simply refuse to risk on the Web. Facebook has taken and continues to take liberties on behalf of their users. Their perception of privacy and their users perception of privacy is often very different. I don't think this is maliciousness on Facebook's part, but it does show me that Facebook is painfully out of touch with the needs and beliefs of their CORE users, who are still wary of the openness that a Web 2.0 lifestyle entails."
It's not clear whether the official Facebook for Android app does the same. We'd be interested to hear from you if you've noticed this with the app.
So - beware: Facebook quite probably has your details. More of them, in fact, than you might have thought.
If you have a friend on Facebook who has used the iPhone app version to access the site, then it's very possible that your private phone numbers - and those of lots of your and their friends - are on the site.
The reason: Facebook's "Contact Sync" feature, which synchronises your friends' Facebook profile pictures with the contacts in your phone.
Except that it doesn't do that on your phone. Oh no. Because that would be wrong, to pull the photos down from Facebook and put them on your phone. That would breach Facebook's terms of service.
Instead, what Facebook's app does it that it imports all the names and phone numbers you have on your (smart)phone, uploads them to Facebook's Phonebook app (got a Facebook account? Here's your Phonebook).
Pause for a moment and go and look at it. Did you know those numbers? Did you collect them? Despite the reassuring phrase there - "Facebook Phonebook displays contacts you have imported from your phone, as well as your Facebook friends" - it's absolutely not true. I know because there are numbers there which I don't have. OK, perhaps the people who own them added them; but that's not clear either. So how did they get there? Because it only takes one person to upload another person's number, and the implication is that it's going to be shared around everywhere.
The implications are huge, and extremely worrying. All it takes is for someone's Facebook account to be hacked (perhaps via their phone being stolen) and lots of personal details are revealed.
Kurt von Moos, who first wrote about this earlier this year (since when Facebook has revised its privacy statement, but not altered what goes on in this way) says that there are a number of reasons to be concerned. As he puts it:
"1) Facebook doesn't warn users that they are uploading their phone's adress book to Facebook. In fact, because Facebook doesn't sync contact numbers or email addresses TO your phone, most users wrongly assume that Facebook Contact Sync only syncs user pictures. In reality though, they are pumping your address book, without your consent."Facebook says you can remove your mobile contacts, but it's not clear that that will remove your mobile if someone else uploads it.
von Moos continues:
"2) Phone numbers are private and valuable. Most people who have entrusted you with their phone numbers assume you will keep them private and safe. If you were to ask your friends, family or co-workers if they are ok with you uploading their private phone numbers to be cross-referenced with other Facebook users, how many of them do you think would be ok with it?"He also points to even more egregious problems: (a) can you be sure how Facebook, or its advertisers or partners or whatever it becomes down the line, will use that data? (b) why is it that Facebook takes all your mobile numbers, rather than matching names of contacts with names of friends? (c) sometimes, it gets the matches wrong - and incorrect (or faked) data that people have given to Facebook as their "contact" details (such as hotels or businesses) gets linked as being a "friend", or the lack of an international dialling prefix messes up the match, and means again that someone who you don't know is identified as a "friend" or contact.
von Moos concludes: "There are some contacts and phone numbers who's privacy I simply refuse to risk on the Web. Facebook has taken and continues to take liberties on behalf of their users. Their perception of privacy and their users perception of privacy is often very different. I don't think this is maliciousness on Facebook's part, but it does show me that Facebook is painfully out of touch with the needs and beliefs of their CORE users, who are still wary of the openness that a Web 2.0 lifestyle entails."
It's not clear whether the official Facebook for Android app does the same. We'd be interested to hear from you if you've noticed this with the app.
So - beware: Facebook quite probably has your details. More of them, in fact, than you might have thought.